Sewing machine sensor light passage - is sealed by transparent plug with convex outer lens surface

摘要

The optical passage to carry the light between a light source and receiver, in the sensor assembly for a sewing machine to monitor the fabric edge or the like, is a drilling in a sliding surface in contact with the material such as the needle plate or presser foot sole. The drilling is closed at the sliding surface by a transparent plug (6) in the form of a lens with at least one convex upper lens surface (7). The convex lens surface (7) pref. projects above the plane of the sliding surface (1a) where the fabric moves. In another form, the convex lens surface is away from the sliding surface (1a), and the lens structure is flush with the sliding surface (1a). The plug (6) is formed from a hardened drop of a transparent plastics material with a composition to give a viscosity and surface tension which, when unhardened, forms a drop with the required convex outer surface (7). ADVANTAGE - The system reduces the gap between the light source and receiver to a min. to prevent light beam loss and the effects of incidental light.